Dendritic polymer, dendritic polymer monomer, and hyperbranched copolymer

ABSTRACT

A dendritic polymer, a dendritic polymer monomer, and a hyperbranched copolymer are described. The dendritic polymer monomer has a structure denoted by Z′-(Q)n-Y, wherein Z′ represents a structure denoted by the following formula (a) and/or formula (b), Q represents a dendritic constitutional repeating unit of the dendritic polymer monomer, n represents the generation number of the dendritic polymer monomer, and is an integer within a range of 2-6, Y represents a group that contains SO 3   −  and COO − , R 14 -R 16  can be identical to or different from each other, and are H or C 1 -C 5  alkyl respectively. The monomer can be used as a copolymerizable monomer for preparing a hyperbranched polymer applicable to oil fields, the obtained hyperbranched polymer can be used as an inhibiting filtrate reducer for drilling fluid, flocculating agent, encapsulating agent, heat-resistant and salinity-resistant polymer flooding agent, and thickening agent for fracturing liquid, etc.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 14/314,756,filed on Jun. 25, 2014, which claims priority to Chinese ApplicationNos. 201310256842.9 and 201310256162.7, both of which filed on Jun. 25,2013, entitled “Hyperbranched Copolymer and Preparation Method and Usethereof” and “Dendritic Polymer, Dendritic Polymer Monomer andPreparation Method and Use thereof,” respectively. The content of eachprior application is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a dendritic polymer, a dendriticpolymer monomer, and a hyperbranched copolymer.

BACKGROUND OF THE INVENTION

In emulsion polymerization field, if emulsion or inverse emulsion isobtained with an appropriate surfactant, the product quality of theapplication system will be greatly improved; however, the residualsurfactant after polymerization reaction will result a series ofproblems. Up to now, some polymerizable surfactants applicable toemulsion polymerization have been proposed in many patent literatures.For example, U.S. Pat. No. 4,939,283 discloses a polymerizablesurfactant obtained from the reaction between a conventional non-ionicsurfactant and allyloxyglycidol ether; U.S. Pat. No. 5,296,627 disclosesan ethylene terminated allyloxypolymerizable surfactant; U.S. Pat. No.6,649,718 discloses a polymerizable surfactant obtained from thereaction between long-chain alkylene oxide and allyl alcohol; U.S. Pat.No. 7,026,418 discloses a surfactant prepared from a copolymer ofalkylene oxide with polymerizable double bonds and glycidol ether;CN102489215A discloses an amphoteric reacting surfactant; CN101982224Adiscloses a polymerizable surfactant that contains allyl or methyl allyland is obtained by etherification between a glycidol ether compound andallyl alcohol or methyl allyl alcohol and follow-up epoxy addition.

In the petroleum drilling course, the encountered formations are moreand more complex, and exceptional wells, ultra-deep wells, and complexwells increase with years, bringing higher requirements for the drillingfluid. In the development of unconventional oil and gas, typically shalegas, 60%˜70% horizontal wells of shale gas in foreign countries employoil base drilling fluid systems for well drilling, to meet therequirement for well wall stability, lubrication and stickingprevention. However, water-based drilling fluids are the best choice,because oil-based drilling fluids have high cost and environmentalpollution problems. It is found in researches that active shale sufferswater loss (or dehydration) in dense CaCl₂ solution, therefore, it isnecessary to study the application of water-based CaCl₂/polymer drillingfluids for horizontal drilling of shale gas for the purpose of costreduction and environmental protection. Since linear polymers can'tfully meet the requirements of well drilling owing to the fact thattheir tackifying ability is degraded under high-salinity conditions, akey task in the development of water-based CaCl₂/polymer drilling fluidsis to develop a polymer treating agent applicable to water-basedCaCl₂/polymer drilling fluids.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a dendritic polymer, adendritic polymer monomer and a hyperbranched copolymer, which caneffectively improve heat resistance, salinity resistance and inhibitionproperties of oil-displacing agents, and can be used for preparation ofa water-based CaCl₂/polymer drilling fluid, and a preparation method anduse thereof.

The present invention provides a dendritic polymer, having a structuredenoted by Z-(Q)n-Y, wherein Z represents a group that can havecondensation reaction with acyl halides; Q represents a dendriticconstitutional repeating unit of the dendritic polymer; n represents thegeneration number of the dendritic polymer, and is an integer within arange of 2-6; and Y represents a group containing SO₃ ⁻ and COO⁻.

Moreover, the present invention provides a dendritic polymer monomerhaving a structure denoted by Z′-(Q)n-Y, wherein Z′ represents astructure denoted by the following formula (a) and/or formula (b); Qrepresents a dendritic constitutional repeating unit of the dendriticpolymer monomer; n represents the generation number of the dendriticpolymer monomer, and is an integer within a range of 2-6; and Yrepresents a group containing SO₃ ⁻ and COO⁻,

R₁₄-R₁₆ are identical to or different from each other, and are H orC₁-C₅ alkyl respectively. Furthermore, the present invention provides ahyperbranched copolymer containing dendritic structural units A,amphoteric ion structural units B, structural units C, and structuralunits D, and calculated in moles, the ratio of dendritic structural unitA:amphoteric ion structural unit B:structural unit C:structural unitD=0.03-0.35:0.03-0.5:0.03-0.3:0.15-0.95, preferably the ratio ofdendritic structural unit A:amphoteric ion structural unit B:structuralunit C:structural unit D=0.05-0.25:0.05-0.3:0.05-0.15:0.25-0.65, and theapparent viscosity of 1 mass % water solution of the hyperbranchedcopolymer is 20-60 mPa·s,

wherein the dendritic structural unit A has a structure denoted byZ′-(Q)n-Y, wherein Z′ represents a structure denoted by the followingformula (a1) and/or formula (a2); Q represents a dendriticconstitutional repeating unit of the dendritic structure; n representsthe generation number of the dendritic structure, and is an integerwithin a range of 2-6; and Y represents a group containing SO₃ ⁻ andCOO⁻,

R₁₄-R₁₆ are identical to or different from each other, and are H orC₁-C₅ alkyl respectively; the amphoteric ion structural unit B has astructure denoted by the following formula (b1) and/or formula (b2),

in formula (b1) and formula (b2), R¹, R², R³, R⁴ and R⁵ are H or C₁-C₃alkyl respectively, m and n are an integer within a range of 0-5respectively, and L is O or NH; in formula (b1), Y is COO⁻ or SO₃ ⁻; informula (b2), X⁻ is halogen anion, and R is H or hydroxyl-substitutedC₁-C₃ alkyl;

the structural unit C has a structure denoted by the following formula(c);

the structural unit D has a structure denoted by the following formula(d).

In formula (c), R⁶, R⁷ and R⁸ are H or C₁-C₃ alkyl respectively; informula (d), R⁹, R¹⁰, R¹¹, R¹² and R^(12′) are H or C₁-C₃ alkylrespectively, T is a bond or

M¹ is H or an alkali metal element, and y is an integer within a rangeof 1-4.

A polymer prepared from coordination of the dendritic polymer anddendritic polymer monomer disclosed in the present invention with othermonomers such as acrylamide can effectively improve heat resistance,salinity resistance and inhibition properties, and water-solubility ofpolymer treating agents for drilling fluids. When the hyperbranchedcopolymer provided in the present invention is used as a treating agentfor a hyperbranched amphoteric ion polymer for drilling fluid, thedrilling fluid can meet the demand for safe well drilling operation inan environment with 100° C. or higher well-bottom temperature and/orhigh salinity (sodium chloride) and high calcium content, therheological property and filtrate loss of a water-based drilling fluidunder high-temperature and high-pressure conditions can be controlled,and the inhibiting ability of the drilling fluid can be improved. Forexample, it can be seen from the outcomes in the attached Table 1: witha polymer treating agent prepared from the dendritic polymer monomerprepared in Preparation Example 3 of the present invention, whenmeasured after aging for 16h at 180° C., the API filtrate loss isreduced to 14.5 ml when compared with 89 ml API filtrate loss in thecase that the dendritic polymer monomer is not added, which means thereduction rate is as high as 83.8%. In addition, the inhibiting abilityR₁ is improved to 96.1% and the viscosity retentivity is improved to34.5%, when compared with the respective 91.5% and 15.2% values in thecase that the dendritic polymer monomer is not added. Moreover, sincethe polymer contains water-soluble groups, it has high water-solubility.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereunder the embodiments of the present invention will be detaillydiscribed. It should be understood that the embodiments described hereare only provided to describe and explain the present invention, butshall not be deemed as constituting any limitation to the presentinvention.

In the present invention, a dendritic polymer is also known as adendronized polymer, which is a linear polymer with a dendron in eachrepeating unit.

The dendritic polymer in the present invention has a structure denotedby Z-(Q)n-Y, wherein Z represents a group that can have condensationreaction with acyl halides, Q represents a dendritic constitutionalrepeating unit of the dendritic polymer; n represents the generationnumber of the dendritic polymer, and is an integer within a range of2-6; and Y represents a group containing SO₃ ⁻ and COO⁻.

Herein the group that can have condensation reaction with acyl halidecan be any known group that can have condensation reaction with acylhalides in the art, and preferably Z is —OH or —NH₂.

In the above formula, Q can be any dendritic structural unit; adendritic structural unit or dendritic repeating unit is a structuralunit or repeating unit that has the above-mentioned dendritic structure;for example, the following structure can be deemed as having a dendriticshape, or can further create a dendritic shape with a NHX group.

According to the present invention, preferably the dendritic polymer inthe present invention has a structure in which Q has a structure denotedby the following formula (I) and Y has a structure denoted by thefollowing formula (II),

in formula (I), R₁ represents C₁-C₅ alkylene; R₂-R₄ can be identical toor different from each other, and are H or C₁-C₅ alkyl respectively; inaddition, for n structures denoted by formula (I), R₁-R₄ can beidentical to or different from each other;

in formula (II), R₈-R₁₃ can be identical to or different from eachother, and are H or C₁-C₅ alkyl respectively; p and q can be identicalto or different from each other, and are an integer within a range of0-5 respectively; and M is H, Na, or K.

In the present invention, the alkyl can be n-alkyl (linear alkyl) oriso-alkyl (branched alkyl).

In the present invention, the alkylene can be n-alkylene (linearalkylene) or iso-alkylene (branched alkylene).

In the present invention, for example, the C₁-C₅ alkylene can bemethylene, ethylidene (—CH₂CH₂—), propylidene (—CH₂CH₂CH₂—),iso-propylidene (—CH(CH₃)CH₂— or —CH₂CH(CH₃)—), butylidene(—CH₂CH₂CH₂CH₂—) or any of its isomers, or amylidene (—CH₂CH₂CH₂CH₂CH₂—)or any of its isomers. Preferably it is ethylidene in the presentinvention.

In the present invention, the C₁-C₅ alkyl can be methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, tertiary butyl, n-pentyl, orneo-pentyl. Preferably it is methyl and/or ethyl.

In the present invention, preferably the dendritic polymer has astructure denoted by the following formula (III) and/or formula (IV),

Z, R₈-R₁₃, M, p, and q are in the same definitions as those describedabove.

Wherein the polymer denoted by formula (III) is a 2G dendritic polymer,i.e. its generation number n is 2; the polymer denoted by formula (IV)is a 3G dendritic polymer, i.e. its generation number n is 3. Thepolymer denoted by formula (III) and the polymer denoted by formula (IV)may be different from each other in terms of the generation number only,or may be different from each other in terms of Z, R₁-R₁₃, M, p, and q.

The dendritic polymer in the present invention, wherein preferably Z isOH; R₁ is CH₂CH₂; R₂-R₁₃ are H respectively; M is Na or K; and both pand q are 0 or 1.

The dendritic polymer monomer provided in the present invention has astructure denoted by Z′-(Q)n-Y, wherein Z′ represents a structuredenoted by the following formula (a) and/or formula (b); Q represents adendritic constitutional repeating unit of the dendritic polymermonomer; n represents the generation number of the dendritic polymermonomer, and is an integer within a range of 2-6; and Y represents agroup containing SO₃ ⁻ and COO⁻,

R₁₄-R₁₆ are identical to or different from each other, and are H orC₁-C₅ alkyl respectively.

The dendritic polymer monomer provided in the present invention, whereinQ can be any dendritic structural unit of the dendritic polymer monomer,and preferably has a structure denoted by the following formula (I), andY has a structure denoted by the following formula (II),

Wherein in formula (I), R₁ represents C₁-C₅ alkylene, R₂-R₄ can beidentical to or different from each other, and are H or C₁-C₅ alkylrespectively; in addition, for n structures denoted by formula (I) R₁-R₄can be identical to or different from each other;

in formula (II), R₈-R₁₃ can be identical to or different from eachother, and are H or C₁-C₅ alkyl respectively; p and q can be identicalto or different from each other, and are an integer within a range of0-5 respectively; and M is H, Na, or K.

In the present invention, preferably the dendritic polymer monomer has astructure denoted by any of the following formula (1), (2), (3) and (4),

R₁-R₄, R₈-R₁₆, M, p, and q are in the same definitions as those in thedendritic polymer described above.

In the present invention, wherein more preferably the dendritic polymermonomer has a structure denoted by the above formula (1) and/or formula(3), and, in formula (1) and formula (3), R₁ is CH₂CH₂; R₂-R₄ and R₈-R₁₆are H; M is Na or K; and both p and q are 0 or 1.

According to a method for preparation of a dendritic polymer provided inthe present invention, the method comprises the following steps if thedendritic polymer has a structure denoted by the above formula (III)and/or formula (IV):

(1) preparing an intermediate of a structure denoted by the followingformula (5) and/or formula (6),

in formula (6), A is

in formula (5) and formula (6), Z represents a group which can havecondensation reaction with acyl halide, preferably Z is OH or NH₂; R₁represents C₁-C₅ alkylene, R₂-R₄ can be identical to or different fromeach other, and are H or C₁-C₅ alkyl respectively; in addition, for nstructures denoted by formula (I), R₁-R₄ can be identical to ordifferent from each other;

(2) under nucleophilic addition reaction conditions, controlling theintermediate to contact with an unsaturated anhydride denoted by thefollowing formula (7), to form carboxylic acid amide that containsunsaturated bonds,

in formula (7), R₈-R₁₃ can be identical to or different from each other,and are H or C₁-C₅ alkyl respectively; p and q can be identical to ordifferent from each other, and are an integer within a range of 0-5respectively;

(3) at 30-100° C. reaction temperature, controlling the carboxylic acidamide that contains unsaturated bonds obtained in step (2) to contactwith sulfurous acid and/or an alkali metal sulphite. The intermediate inthe structure denoted by formula (5) and/or formula (6) can be preparedwith a known method in the art; for example, the intermediate in thestructure denoted by formula (5) can be obtained by controlling anunsaturated acid alkyl ester to have Michael addition reaction with theamine in Z—R₁—NH₂, then controlling the product of the Michael additionreaction to have condensation reaction with the alkyl diamine inNH₂-R₁—NH₂, and then controlling the product of the condensationreaction to have the Michael addition reaction and condensation reactiondescribed above repeatedly in sequence to obtain a polymer intermediatein a dendritic structure, the number of repetitions corresponds to therequired generation number.

wherein Z, R₁, R₁₄-R₁₆ are in the same definitions as those describedabove, R′ is preferably C₁-C₅ alkyl, more preferably methyl or ethyl.

The Michael addition reaction preferably happens in the existence of asolvent, which is preferably one or more of methanol, ethanol,isopropanol, and tert-butyl alcohol.

The conditions of the Michael addition reaction can include: 25-55° C.reaction temperature, and 3-7h reaction time, preferably 4-6h reactiontime.

The condensation reaction preferably happens in the existence of asolvent, which is preferably one or more of methanol, ethanol,isopropanol, and tert-butyl alcohol.

The conditions of the condensation reaction can include: 10-60° C.reaction temperature, and 20-35h reaction time, preferably 24-30hreaction time.

Hereunder the preparation of an intermediate will be described in anexample of the intermediate denoted by formula (5d).

According to a preferred embodiment of the present invention, theintermediate denoted by formula (5d) can be prepared with a method thatcomprises the following steps:

(I) adding methyl acrylate, ethanolamine, and a solvent (e.g., methanol)into a reactor, stirring for 10-60 min while filling a shielding gas(e.g., N₂) into the reactor at 10-25° C., and then heating up to 30-40°C. and keeping for 3-7h at that temperature, and carrying out reducedpressure distillation to remove the organic solvent, so as to obtain aproduct in the structure denoted by formula (5a);

(II) loading the product in the structure denoted by formula (5a) and anorganic solvent (e.g., methanol) into a reactor, adding ethylene diaminein droplets while stirring at 10-40° C., controlling the reactants toreact for 20-35h at that temperature, and then carrying out reducedpressure distillation to remove the organic solvent, so as to obtain anintermediate product in the structure denoted by formula (5b);

(III) loading the intermediate product in the structure denoted byformula (5b) and an organic solvent (e.g., methanol) into a reactor,adding methyl acrylate in droplets while stirring at 10-40° C.,controlling the reactants to react for 20-35h at that temperature, andthen carrying out reduced pressure distillation to remove the organicsolvent, so as to obtain an intermediate product in the structuredenoted by formula (5c);

(IV) loading the intermediate product in the structure denoted byformula (5c) and an organic solvent (e.g., methanol) into a reactor,adding ethylene diamine in droplets while stirring at 10-40° C.,controlling the reactants to react for 20-35h at that temperature, andthen carrying out reduced pressure distillation to remove the methanol,so as to obtain an intermediate product in the structure denoted byformula (5d).

The above step (III) and step (IV) can be repeated to evolve ageneration, so as to obtain an intermediate in the structure denoted byformula (6).

In formula (5) and formula (6), if R₁-R₄ are other substituents, theintermediate can be prepared similarly with the method described above,provided that appropriate raw materials are selected.

According to the preparation method provided in the present invention,if the solvents used in the steps are the same, the next step ofreaction can be executed directly without removing the solvent.

In step (2), the unsaturated anhydride can be denoted by the followingstructural formula:

Wherein R₈-R₁₃, p and q are in the same definitions as those describedabove.

Preferably, the unsaturated anhydride is maleic anhydride.

The conditions of the nucleophilic addition reaction in step (2)include: 60-100° C. reaction temperature, preferably 80° C., and 4-20hreaction time.

The step (2) is executed preferably under stirring condition, morepreferably in the existence of an organic solvent such as an amidesolvent and/or haloalkane solvent, further more preferably in theexistence of one or more of N,N-dimethyl formamide, N,N-dimethylacetamide, dichloromethane, trichloromethane, dichloroethane, and methylbenzene. The unsaturated anhydride is preferably added in droplets.

The reaction in step (3) happens preferably in the existence of asolvent, which is preferably an amide solvent and/or haloalkane solvent,more preferably is one or more of N,N-dimethyl formamide, N,N-dimethylacetamide, dichloromethane, trichloromethane, dichloroethane, and methylbenzene. The organic solvent in step (2) can be identical to ordifferent from the organic solvent in step (3); preferably the organicsolvent in step (2) is identical to the organic solvent in step (3).More preferably, the reaction product in step (2) is directly used inthe reaction in step (3) without separation.

The conditions of the contact reaction in step (3) can include: 30-70°C. reaction temperature and 3-20h reaction time. The reaction time canbe determined by judging the time when the double bonds have disappearedcompletely. Whether the double bonds have disappeared completely can bejudged by means of bromide addition (please see chemical books fordetails, or with the method for determining free acrylic acid or brominevalue as described in GB/T10533-2000 “Water TreatmentChemicals—Polyacrylic Acid” or GB/T10535-1997 “Water TreatmentChemicals—Hydrolyzed Polymaleic Anhydride”. In the embodiments of thepresent invention, whether the double bonds have disappeared completelyis judged with the method for determining free acrylic acid or brominevalue as described in GB/T10533-2000 “Water TreatmentChemicals—Polyacrylic Acid”).

After the reaction in step (3) is completed, the obtained mixture isfiltered and the organic solvent is distilled off; then active carbon isadded to make adsorption treatment for 14-28h to remove impurities; thenthe active carbon is filtered off, and the obtained solution isdehydrated in vacuum, to obtain the target dendritic polymer.

The method for preparation of a dendritic polymer monomer provided inthe present invention comprises preparing a dendritic polymer with themethod described above, and then controlling the dendritic polymer tocontact with an unsaturated acyl halide under the conditions ofcondensation reaction.

The contact reaction between the dendritic polymer and the unsaturatedacyl halide preferably happens in the existence of a solvent, and thecontact conditions can include: 0-20° C. reaction temperature and0.5-10h reaction time.

According to a preferred embodiment of the present invention, the methodfor preparation of a dendritic polymer monomer can comprise thefollowing steps: loading the dendritic polymer, an organic solvent, andan acid binding agent into a reaction bulb equipped with a coolingdevice, cooling the mixture down to about 5° C., adding an unsaturatedacyl halide slowly (the temperature is controlled to be not higher than15° C. in the adding process), and then keeping the reaction for 0.5-8hat about 10° C.; keeping the reactants in still state to separate theorganic phase, neutralizing and washing with saturated sodiumbicarbonate solution for several times, drying with anhydrous sodiumsulfate, and distilling off the organic solvent to obtain a crudeproduct, and then purifying the crude product to obtain polymerizedproduct, i.e., the expected dendritic polymer monomer.

The unsaturated acyl halide can be unsaturated acyl chloride and/orunsaturated acyl bromide, and preferably the molecule of the unsaturatedacyl halide contains 3-6 carbon atoms; particularly, in the presentinvention, the unsaturation acyl halide is acryloyl chloride and/ormethacrylic chloride.

The acid binding agent can be any alkaline substance, preferably is anorganic nitrogen containing compound, more preferably is one or more ofmethylamine, ethylamine, propylamine, dimethylamine, diethylamine,triethylamine, tri-n-propylamine, tri-n-butylamine, and pyridine.

The mole ratio of the dendritic polymer:organic solvent:acid bindingagent:unsaturated acyl halide is preferably 1:18-22:1.0-1.1:1.0-1.05.

Since all the reactions involved in the preparation method describedabove are ordinary organic chemical reactions and the direction of eachreaction is deterministic and unique, the progress of the reactions canbe determined according to the raw materials and conditions of thereactions, without characterizing the products separately. Of course,the synthesis of intermediate products, intermediates, and targetproducts can be determined by conventional means, such as infrareddetection, nuclear magnetic resonance detection, or mass spectrometricdetection, etc.

Also, the present invention discloses an application of the dendriticpolymer and dendritic polymer monomer in preparation of filtratereducers for drilling fluids, oil-displacing agents, thickening agentsfor fracturing liquids, and oil field water treatment agents.

In the hyperbranched copolymer provided in the present invention, thetotal weight of the dendritic structural unit A, amphoteric ionstructural unit B, structural unit C, and structural unit D accounts for90% or more in the total weight of the hyperbranched polymer.

More preferably, the dendritic structural unit A has a structure denotedby any of the following formula (A1), (A2), (A3), and (A4),

R₁-R₄, R₈-R₁₆, M, p and q are in the same definitions are thosedescribed above.

More preferably, the dendritic structural unit A has a structure denotedby formula (1) and/or formula (3), and, in formula (1) and formula (3),R₁ is CH₂CH₂; R₂-R₄ and R₈-R₁₆ are H respectively; M is Na; and both pand q are 0.

According to the present invention, the X⁻ in the amphoteric ionstructural unit B can be any halogen anion, such as Cl⁻, Br⁻, or F, andcan be the same or different among different structural units of thesame polymer.

The hydroxy-substituted C₁-C₃ alkyl can be —CH(OH)CH₃, —CH(OH)C₂H₅, or—CH(OH)C₃H₇, for example.

In the hyperbranched copolymer in the present invention, the amphotericion structural unit B is one or more of the structures denoted by thefollowing formulae,

According to the present invention, the structural unit C can be in thestructure denoted by formula (C) in which R₆ is H, methyl, ethyl orpropyl and R₇ and R₃ are H respectively, or R₈ is H, methyl, ethyl orpropyl and R₇ and R₆ are H respectively; preferably, the structural unitC is in the structure denoted by formula (C) in which R₈ is H or methyland R₇ and R₆ are H respectively (i.e, an acrylamide structural unit ora methyl acrylamide structural unit).

In the hyperbranched copolymer in the present invention, preferably thestructural unit D is in a structure denoted by at least one of thefollowing structural formulae,

wherein M¹ is H or an alkali metal element.

The alkali metal element can be one or more of Li, Na, and K.Preferably, M¹ is H, K, or Na. M¹ can be the same or different amongdifferent structural units of the same polymer.

Also, the present invention provides a method for preparation of ahyperbranched copolymer, comprising: under the conditions of solutionpolymerization, controlling a dendritic polymer monomer I, an amphotericion monomer II, a monomer III, and a monomer IV to contact with anoxidation-reduction initiating agent in a neutral or alkalineenvironment, wherein

the dendritic polymer monomer I is the dendritic polymer describedabove;

the amphoteric ion monomer II has a structure denoted by the followingformula (ii1) and/or formula (ii2), the monomer III has a structuredenoted by the following formula (iii), and the monomer IV has astructure denoted by the following formula (iv),

in formula (ii1) and formula (ii2), R¹, R², R³, R⁴ and R⁵ are H or C₁-C₃alkyl or iso-alkyl respectively, m and n are an integer within a rangeof 0-5 respectively, and L is O or NH; in formula Y is COO⁻ or SO₃ ⁻; informula (ii2), X⁻ is halogen anion, and R is H or hydroxyl-substitutedC₁-C₃ alkyl,

in formula (iii), R⁶, R⁷ and R⁸ are H or C₁-C₃ alkyl respectively,

in formula (iv), R⁹, R¹⁰, R¹¹, and R^(12′) are H or C₁-C₃ alkyl; R¹² isa bond or C₁-C₁₂ linear or branched alkylene; T is a bond or

M¹ is H or an alkali metal element; and y is an integer within a rangeof 1-4;

in addition, calculated in moles, the ratio of dendritic polymer monomerI:amphoteric ion monomer II:monomer III:monomer IV is0.03-0.35:0.03-0.5:0.03-0.3:0.15-0.95, and the contact conditions aredetermined in a way that the apparent viscosity of 1 mass % watersolution of the obtained polymer is 20-60 mPa·s.

Preferably, Q is in a structure denoted by the following formula (I),and Y is in a structure denoted by the following formula (II),

Wherein in formula (I), R₁ represents C₁-C₅ alkylene, R₂-R₄ can beidentical to or different from each other, and are H or C₁-C₅ alkylrespectively; in addition, for n structures denoted by formula (I),R₁-R₄ can be identical to or different from each other;

in formula (II), R₈-R₁₃ can be identical to or different from eachother, and are H or C₁-C₅ alkyl respectively; p and q can be identicalto or different from each other, and are an integer within a range of0-5 respectively; and M is H, Na, or K.

More preferably, the dendritic polymer monomer I has a structure denotedby any of the formula (A1), (A2), (A3), and (A4) as described above.

According to the preparation method disclosed in the present invention,wherein the dendritic polymer monomer I has a structure denoted byformula (1) and/or formula (3), and, in formula (1) and formula (3), R₁is CH₂CH₂; R₂-R₄ and R₈-R₁₃ are H respectively; M is Na; and both p andq are 0.

In the present invention, preferably the amphoteric ion monomer II isone or more of the structures denoted by the following formulae,

More preferably, the amphoteric ion monomer II is one or more selectedfrom the group consisting of 3-acrylamide propyl dimethyl ammoniumpropylsulfonate, 3-acrylamide propyl (2-hydroxy)-propyl dimethylammonium chloride, 3-acryloxy ethyl dimethyl ammonium propylsulfonate,3-acryloxy ethyl diethyl ammonium propylsulfonate, 3-acryloxy ethyldiisopropyl ammonium propylsulfonate, 3-acrylamide propyl trimethylammonium chloride, and 3-acryloxy propyl trimethyl ammonium chloride.

According to the present invention, the monomer III can be in thestructure denoted by formula (iii) in which R₆ is H, methyl, ethyl orpropyl, and R₇ and R₈ are H respectively, or R₈ is H, methyl, ethyl orpropyl and R₇ and R₆ are H respectively; more preferably, the monomerIII is in the structure denoted by formula (iii) in which R₈ is H ormethyl and R₇ and R₆ are H respectively (i.e., acrylamide or methylacrylamide).

According to a method for preparation of a hyperbranched polymerdisclosed in the present invention, the monomer IV is in a structuredenoted by at least one of the following structural formulae,

wherein M¹ is H or an alkali metal element. The alkali metal element canbe one or more of Li, Na, and K.

According to the preparation method disclosed in the present invention,wherein the solution polymerization conditions include: initialtemperature of polymerization can be 20-80° C., preferably 30-60° C.;polymerization reaction time can be 20-100 min, preferably 30-90 min.

In the present invention, the pH value of the neutral or alkalineenvironment is preferably 7-10. The neutral or alkaline environment canbe obtained with 10-20 wt % sodium hydroxide and/or potassium hydroxidesolution.

Preferably the solvent used in solution polymerization is water. Morepreferably, in relation to 0.05-0.25 mole dendritic polymer monomer, theusage of water is 95-200 ml, and the usage of the oxidation-reductioninitiating agent is 0.2-1.2 g.

The oxidation-reduction initiating agent can be any knownoxidation-reduction initiating agent in the domain of polymers;preferably, in the oxidation-reduction initiating agent, the oxidizingagent is potassium persulfate and/or ammonium persulfate, and thereducing agent is one of sodium bisulfite, sodium pyrosulfite, sodiumsulfite, and sodium thiosulfate.

Preferably, the method for preparation of a hyperbranched polymerdisclosed in the present invention further comprises: shearing, drying,and grinding the gelatinous elastic product obtained from the contactreaction in sequence. The drying is preferably carried out at 100-120°C. temperature, and the degree of grinding is determined according tothe actual requirement. The shearing, drying, and grinding proceduresare known by those skilled in the art, and will not be detailed furtherhere.

According to a preferred embodiment of the present invention, the methodfor preparation of a hyperbranched copolymer comprises the followingsteps:

(i) loading water and sodium hydroxide and/or potassium hydroxide in thesame moles as a monomer III into a reactor; adding monomer III afterthey are dissolved, and stirring till the monomer III is dissolvedcompletely; adding the dendritic polymer monomer I, amphoteric ionmonomer II, monomer IV, and stirring to a homogeneous state; adjustingthe pH value of the system to 7.0-10.0 with 10-20 mass % sodiumhydroxide and/or potassium hydroxide solution;

(ii) transferring the reaction mixture prepared in step (i) into apolymer reactor; adding an oxidation-reduction initiating agent whilestirring; controlling the initial temperature of polymerization reactionat 20-80° C., preferably 30-60° C., and keeping the polymerizationreaction for 20-100 min, preferably 30-90 min, more preferably 45-90min, to obtain a gelatinous elastic product;

(iii) shearing the gelatinous elastomer obtained in step (ii), drying itat 100-120° C. preferably, and grinding it to obtain a hyperbranchedcopolymer that can be used as a polymer treating agent for drillingfluids.

wherein the proportions of the raw materials are in the same definitionsas those described above, preferably the proportions of the rawmaterials are:

dendritic polymer monomer I: 0.05˜0.25 mole

amphoteric ion monomer II: 0.05˜0.30 mole

monomer III: 0.005˜0.15 mole

monomer IV: 0.25˜0.65 mole

initiating agent (composed of oxidizing agent and reducing agent):0.10˜0.6 g each

water: 95˜200 ml

Also, the present invention provides a copolymer obtained with themethod described above.

Also, the present invention discloses an application of the copolymer indrilling fluids.

Preferably, the copolymer is used as a polymer treating agent fordrilling fluids.

When the copolymer provided in the present invention is used as apolymer treating agent for drilling fluids, it exhibits highheat-resistant and salinity-resistant properties, as well as highinhibiting ability, and the product has excellent water-solubility. Ifthe copolymer is prepared with a rapid polymerization method in a watersolution, the reaction process can be controlled easily, the operationis easy, the product quality is stable, the energy consumption is verylow in the production and drying procedures, and there is noenvironmental pollution. The copolymer has a favorable filtrate lossreducing property in saturated brine at 180° C. temperature andhigh-calcium environments, and has no adverse effect to the rheologicalproperty and filtrate loss of drilling fluid while ensuring enoughinhibiting ability. The main reason for such favorable properties may bethat the molecules of the dendritic polymer monomer used in the presentinvention contain acryloxy that is helpful for polymerization and themolecular chain of the monomer contains amino, carboxy, and sulfonicgroups; thus, a hyperbranched polymer can be obtained when the monomeris copolymerized with other monomers. When the hyperbranched polymer isused as a treating agent for drilling fluid, the tackifying effect andstability of the polymer at high temperatures can be improved, owing tothe hyperbranched structure of the polymer; since the molecular chain ofthe large hyperbranched monomer contains amido, carboxy, and sulfonicgroups, the hyperbranched polymer has favorable tackifying effect,filtrate loss reducing effect, and inhibiting ability against hydrationswelling of shale or clay, when it is used in a drilling fluid.

In the present invention, the apparent viscosity of 1 mass % watersolution of the hyperbranched copolymer is measured at 25° C. with aFann-35 rotary viscosimeter. The contents of the structural units in thehyperbranched copolymer are calculated on the basis of the usages of themonomers.

Hereunder the present invention will be further detailed in someembodiments.

Preparation Example 1 Synthesis of Intermediate

First, an intermediate is synthesized with the conventional method:

(I) methyl acrylate, ethanolamine, and methanol are added at a moleratio of 1:0.5:15 into a reactor, the mixture is stirred for 30 min atroom temperature while N₂ is filled, and then is heated up to 35° C. andheld for 4h; then, the mixture is treated by reduced pressuredistillation to remove the methanol, so as to obtain a product in thestructure denoted by formula (5a);

(II) the product in the structure denoted by formula (5a) and methanolare added at a weight ratio of 1:3 into a reactor, ethylene diamine isadded in droplets (the mole ratio of the product in the structuredenoted by formula (5a):ethylene diamine is 0.5:1.05) at 25° C. whilestirring, the reaction is maintained for 24h, and then the mixture istreated by reduced pressure distillation to remove the methanol, so asto obtain an intermediate product in the structure denoted by formula(5b);

(III) the intermediate product in the structure denoted by formula (5b)and methanol are added at a weight ratio of 1:3 into a reactor, methylacrylate is added in droplets (the mole ratio of the product in thestructure denoted by formula (5a):methyl acrylate is 0.25:1.05) at 25°C. while stirring, the reaction is maintained for 24h, and then themixture is treated by reduced pressure distillation to remove themethanol, so as to obtain an intermediate product in the structuredenoted by formula (5c); (IV) the intermediate product in the structuredenoted by formula (5c) and methanol are added at a weight ratio of 1:3into a reactor, ethylene diamine is added in droplets (the mole ratio ofthe product in the structure denoted by formula (5a):ethylene diamine is0.25:1.05) at 25° C. while stirring, the reaction is maintained for 24h,and then the mixture is treated by reduced pressure distillation toremove the methanol, so as to obtain an intermediate in the structuredenoted by formula (5d);

Preparation Example 2 Synthesis of Intermediate

First, an intermediate is synthesized with the conventional method:

(I) methyl acrylate, ethanolamine, and methanol are added at a moleratio of 1:0.50:10 into a reactor, the mixture is stirred for 30 min atroom temperature while N₂ is filled, and then is heated up to 35° C. andheld for 4h; then the mixture is treated by reduced pressuredistillation to remove the methanol, so as to obtain a product in thestructure denoted by formula (5a);

(II) the product in the structure denoted by formula (5a) and methanolare added at a weight ratio of 1:3.5 into a reactor, ethylene diamine isadded in droplets (the mole ratio of the product in the structuredenoted by formula (5a):ethylene diamine is 0.5:1.0) at 25° C. whilestirring, the reaction is maintained for 24h, and then the mixture istreated by reduced pressure distillation to remove the methanol, so asto obtain an intermediate product in the structure denoted by formula(5b);

(III) the intermediate product in the structure denoted by formula (5b)and methanol are added at a weight ratio of 1:3.5 into a reactor, methylacrylate is added in droplets while stirring at 25° C., the reactantsare controlled to react for 24h at that temperature, and then themixture is treated by reduced pressure distillation to remove themethanol, so as to obtain an intermediate product in the structuredenoted by formula (5c);

(IV) the intermediate product in the structure denoted by formula (5c)and methanol are added at a weight ratio of 1:3.5 into a reactor,ethylene diamine is added in droplets while stirring at 25° C., thereactants are controlled to react for 24h at that temperature, and thenthe mixture is treated by reduced pressure distillation to remove themethanol, so as to obtain an intermediate product in the structuredenoted by formula (5d);

(V) the intermediate product in the structure denoted by formula (5d)and methanol are added at a weight ratio of 1:3.5 into a reactor, methylacrylate is added in droplets while stirring at 25° C., the reactantsare controlled to react for 24h at that temperature, and then themixture is treated by reduced pressure distillation to remove themethanol, so as to obtain an intermediate product in the structuredenoted by the following formula (6e) (similar to formula (5c), but thegeneration number is increased by 1);

(VI) the intermediate product obtained in step (V) and methanol areadded at a weight ratio of 1:3.5 into a reactor, ethylene diamine isadded in droplets while stirring at 25° C., the reactants are controlledto react for 24h at that temperature, and then the mixture is treated byreduced pressure distillation to remove the methanol, so as to obtain anintermediate in the structure denoted by the following formula (6f).

Preparation Example 3 Preparation of Dendritic Polymer Monomer

(1) 74.5 g intermediate product in the structure denoted by formula (5d)obtained in the Preparation Example 1 and 180 ml N,N-dimethyl acetamideare added into a reactor, a solution prepared by dissolving 39.2 gmaleic anhydride (MA) in 100 ml N,N-dimethyl acetamide is added indroplets at 25° C. while stirring, and then the reactants are heated upto 80° C. and controlled to react for 20h at that temperature;

(2) 336 g 15 mass % sodium sulfite water solution is added into thereaction product at 30° C., and the reactants are controlled to reactfor 20h, till the double bonds disappear (judged by means of bromideaddition); then, the reaction product is filtered, and the organicsolvent is distilled off; active carbon is added for 24h absorptiontreatment; then, the active carbon is filtered off, and the obtainedsolution is treated by dehydration in vacuum, to obtain a hyperbranchedproduct in the structure denoted by the following formula (I-1):

wherein:

(3) the hyperbranched product obtained in step (2), an organic solvent(dichloromethane), and an acid binding agent (triethylamine) are addedinto a reaction bulb equipped with a cooling device, the mixture iscooled down to 5° C., and acryloyl chloride is added slowly (theacryloyl chloride is dissolved in a solvent in advance, and thetemperature is controlled to be not higher than 15° C. in the addingprocess), the mole ratio of hyperbranched product:organic solvent:acidbinding agent:acryloyl chloride is 1:18:1:1; then, the reactants arecontrolled to react for 0.5h at 10° C. after the acryloyl chloride wasadded; the reactants are kept in still state to separate the organicphase, the organic phase is neutralized and washed with saturated sodiumbicarbonate solution for several times, and dried with anhydrous sodiumsulfate; then, the organic solvent is distilled off to obtain a crudeproduct; next, the crude product is purified to obtain a polymerizeddendritic polymer monomer product in the structure denoted by formula(1-1), wherein R₁ is CH₂CH₂; R₂-R₄ and R₈-R₁₃ are H respectively; M isNa, and both p and q are 0,

wherein R and R1 are in the same definitions as those described forformula (I-1).

Preparation Example 4 Preparation of Dendritic Polymer Monomer

(1) 74.5 g intermediate product in the structure denoted by formula (5d)obtained in the Preparation Example 1 and 150 ml N,N-dimethyl formamideare added into a reactor, a solution prepared by dissolving 39.2 gmaleic anhydride (MA) in 110 ml N,N-dimethyl formamide is added indroplets at 30° C. while stirring, the reactants are heated up to 90° C.and controlled to react for 8h at that temperature;

(2) 421 g 15 mass % potassium sulfite water solution is added into thereaction product at 70° C., and the reactants are controlled to reactfor 3h, till the double bonds disappear (judged by means of bromideaddition); then, the reaction product is filtered, and the organicsolvent is distilled off; active carbon is added for 24h absorptiontreatment; then, the active carbon is filtered off, and the obtainedsolution is treated by dehydration in vacuum, to obtain a hyperbranchedproduct in the structure denoted by the following formula (I-2):

wherein:

(3) the hyperbranched product obtained in step (2), an organic solvent(N,N-dimethyl acetamide), and an acid binding agent (pyridine) are addedinto a reaction bulb equipped with a cooling device, the mixture iscooled down to 8° C., and methacrylic chloride is added slowly (themethacrylic chloride is dissolved in a solvent in advance, and thetemperature is controlled to be not higher than 15° C. in the addingprocess), the mole ratio of the hyperbranched product:organicsolvent:acid binding agent:acryloyl chloride is 1:20:1.05:1.02; then,the reactants are controlled to react for 0.5h at 10° C.; the reactantsare kept in still state to separate the organic phase, the organic phaseis neutralized and washed with saturated sodium bicarbonate solution forseveral times, and dried with anhydrous sodium sulfate; then, theorganic solvent is distilled off to obtain a crude product; next, thecrude product is purified to obtain a polymerized dendritic polymermonomer product in the structure denoted by formula (2-2), wherein R₁ isCH₂CH₂; R₂-R₄ and R₈-R₁₃ are H respectively; M is K; and both p and qare 0,

wherein R and R1 are in the same definitions as those described forformula (I-2).

Preparation Example 5 Preparation of Dendritic Polymer Monomer

(1) 74.5 g intermediate product in the structure denoted by formula (5d)obtained in the Preparation Example 1 and 150 ml N,N-dimethyl acetamideare added into a reactor, a solution prepared by dissolving 56.9 g3-hexene anhydride in 150 ml N,N-dimethyl acetamide is added in dropletsat 25° C. while stirring, the reactants are heated up to 80° C. andcontrolled to react for 18h at that temperature;

(2) 336 g 15 mass % sodium sulfite water solution is added into thereaction product, and the reactants are controlled to react, till thedouble bonds disappear (judged by means of bromide addition); then, thereaction product is filtered, and the organic solvent is distilled off;active carbon is added for 24h absorption treatment; then, the activecarbon is filtered off, and the obtained solution is treated bydehydration in vacuum, to obtain a hyperbranched product in thestructure denoted by the following formula (I-3):

wherein:

(3) the hyperbranched product obtained in step (2), an organic solvent(methyl benzene), and an acid binding agent (triethylamine) are addedinto a reaction bulb equipped with a cooling device, the mixture iscooled down to 0° C., and acroloyl bromide is added slowly (the acroloylbromide is dissolved in a solvent in advance, and the temperature iscontrolled to be not higher than 15° C. in the adding process), the moleratio of the hyperbranched product:organic solvent:acid bindingagent:acryloyl bromide is 1:22:1.1:1.05; then the reactants arecontrolled to react for 0.5h at 10° C.; the reactants are kept in stillstate to separate the organic phase, the organic phase is neutralizedand washed with saturated sodium bicarbonate solution for several times,and dried with anhydrous sodium sulfate; then the organic solvent isdistilled off to obtain a crude product; next the crude product ispurified to obtain a polymerized dendritic polymer monomer product inthe structure denoted by formula (2-3), wherein R₁ is CH₂CH₂; R₂-R₄ andR₈-R₁₃ are H respectively; M is Na; and both p and q are 1,

wherein R and R1 are in the same definitions as those described forformula (I-3).

Preparation Example 6 Preparation of Dendritic Polymer Monomer

(1) 82.85 g intermediate in the structure denoted by formula (6f)obtained in the Preparation Example 2 and 200 ml N,N-dimethyl acetamideare added into a reactor, a solution prepared by dissolving 39.2 gmaleic anhydride (MA) in 120 ml N,N-dimethyl acetamide is added indroplets at 25° C. while stirring, the reactants are heated up to 80° C.and controlled to react for 15h at that temperature;

(2) 336 g 15 mass % sodium sulfite water solution is added into thereaction product at 60° C., and the reactants are controlled to reactfor 18h, till the double bonds disappear (judged by means of bromideaddition); then, the reaction product is filtered, and the organicsolvent is distilled off; active carbon is added for 24h absorptiontreatment; then, the active carbon is filtered off, and the obtainedsolution is treated by dehydration in vacuum, to obtain a hyperbranchedproduct in the structure denoted by the following formula (I-4):

wherein:

(3) the hyperbranched product obtained in step (2), an organic solvent(dichloromethane), and an acid binding agent (triethylamine) are addedinto a reaction bulb equipped with a cooling device, the mixture iscooled down to 5° C., and acryloyl chloride is added slowly (theacryloyl chloride is dissolved in a solvent in advance, and thetemperature is controlled to be not higher than 15° C. in the addingprocess), the mole ratio of the hyperbranched product:organicsolvent:acid binding agent:acryloyl chloride=1:18:1:1; then thereactants are controlled to react for 0.5h at 10° C.; the reactants arekept in still state to separate the organic phase, the organic phase isneutralized and washed with saturated sodium bicarbonate solution forseveral times, and dried with anhydrous sodium sulfate; then, theorganic solvent is distilled off to obtain a crude product; next thecrude product is purified to obtain a polymerized dendritic polymermonomer product in the structure denoted by formula (2-4), wherein R₁ isCH₂CH₂; R₂-R₄ and R₈-R₁₃ are H respectively; M is Na; and both p and qare 0,

wherein R and R1 are in the same definitions as those described forformula (I-4).

Example 1 Preparation of Hyperbranched Copolymer

200 ml water and 0.05 mole sodium hydroxide are loaded into a reactor;after they are dissolved, 0.05 mole 2-acrylamide-2-methylpropanesulfonic acid is added and the mixture is stirred to homogeneousstate; the pH value of the system is adjusted to 10.0 with 20 mass %sodium hydroxide solution; then, 0.25 mole dendritic polymer monomerprepared in the Preparation Example 3, 0.05 mole 3-acrylamide propyldimethyl ammonium propylsulfonate, and 0.65 mole acrylamide are added,and the mixture is stirred to facilitate dissolving, so as to obtain areaction mixture solution; the reaction mixture solution is transferredinto a polymerization reactor, and 0.10 g ammonium persulfate and 0.10 gsodium bisulfite are added while stirring; the initial temperature ofpolymerization reaction is controlled at 60° C., and the reaction ismaintained for 45 min to obtain a gelatinous elastic product; theobtained gelatinous elastomer is sheared, dried at 120° C., and ground,to obtain a polymer treating agent for drilling fluids. The apparentviscosity of 1 mass % water solution of the polymer treating agent fordrilling fluids is 58.5 mPa·s.

The heat-resistance and salinity-resistance of the polymer treatingagent is evaluated by testing the filtrate loss reduction property incompounding brine. The base mud of compounding brine is prepared asfollows: 15.75 g sodium chloride, 1.75 g anhydrous calcium chloride, 4.6g magnesium chloride, 52.5 g calcium bentonite (an industrial productfrom Weifang Haoda Bentonite Co. Ltd.), and 3.15 g anhydrous sodiumcarbonate are added into 350 ml distilled water, the mixture is stirredfor 20 min at a high speed, and held for 24h at room temperature, toobtain a base mud of compounding brine. In the evaluation process, 1.5wt % specimen is added, the mixture is stirred for 5 min at a highspeed, and then treated by rolled aging for 16h at 180° C. and cooled toroom temperature; then the filtrate loss of the drilling fluid ismeasured with a ZNS drilling fluid filtration press. The API filtrateloss is 228 ml after the base mud is treated by rolled aging for 16h at180° C. The inhibiting ability and adsorptive capacity of the polymertreating agent are tested with a rolling recovery method for shale. Themethod is as follows:

Primary recovery rate R₁: 50 g shale debris sample (m) is weighedaccurately, and added into 350 ml 0.3 mass % polymer solution to bemeasured; then, the solution is loaded into an aging can, sealed, androlled for 16h at 120° C.; next, the solution is cooled down, and thedebris is recovered through a 40-mesh sieve; the recovered debris isbaked at 100±5° C. to constant mass, and is weighed (m₁); then theprimary recovery rate R₁ is calculated. The primary recovery ratereflects the hydration dispersion of the shale in the water solution oftreating agent; the higher the primary recovery rate R₁ is, the higherthe inhibiting ability will be.

Secondary recovery rate R₂: the debris (m₁) obtained in the primaryrecovery process is added into 350 ml clean water, the mixture is rolledfor 2h at 120° C. and then is cooled down, the debris is recoveredthrough a 40-mesh sieve, the recovered debris is baked at 100±5° C. toconstant mass, and then is weighed (m₂); next the secondary recoveryrate R₂ is calculated. The secondary recovery rate reflects thestability of the debris obtained in the primary recovery process inclean water; the higher the secondary recovery rate is, the higher theadsorptive capacity of the treating agent will be.

The debris is obtained at 2,695m in open well 9-5 (at 6-10-mesh size).The recovery rate of the clean water (without specimen) for debris is49.5%.

The calculation formulae are as follows:

${R_{1} = {\frac{m_{1}}{m} \times 100\%}},{R_{2} = {\frac{m_{2}}{m_{1}} \times 100\%}},{R = {\frac{R_{2}}{R_{1}} \times 100\%}}$

wherein R is a relative recovery rate, which reflects the adsorptivecapacity of the polymer on the shale; the higher the value is, thehigher the adsorptive capacity will be.

The solubility is judged on the basis of the time of high speed stirringrequired for forming homogeneous water solution (i.e., without swellingparticles of polymer) when 0.5 mass % water solution of the polymer isprepared at room temperature. The process is as follows: 2 g specimen isadded into 398 ml water while stirring at a high speed, and then thestirring is continued; after the mixing time reaches 3 min, thedissolution state is observed once every 30s, till the specimen isdissolved completely; finally, the mixing time required for completedissolution is recorded.

The tackifying ability of CaCl₂ solution is evaluated on the basis ofthe viscosity ratio of 0.3 mass % CaCl₂ water solution of the polymer(with 20% mass CaCl₂) vs. water solution of the polymer, i.e. theviscosity retentivity:

${{Viscosity}\mspace{14mu} {retentivity}} = {\frac{\begin{matrix}{{Viscosity}\mspace{14mu} {of}\mspace{14mu} {CaCl}_{2}\mspace{14mu} {water}} \\{{solution}\mspace{14mu} {of}\mspace{14mu} {the}\mspace{14mu} {polymer}}\end{matrix}\mspace{14mu}}{\begin{matrix}{{{Viscosity}\mspace{14mu} {of}\mspace{14mu} {water}\mspace{14mu} {solution}}\mspace{11mu}} \\{{of}\mspace{14mu} {the}\mspace{14mu} {polymer}}\end{matrix}\;} \times 100\%}$

The test result is shown in Table 1 below.

Example 2 Preparation of Hyperbranched Copolymer

95 ml water and 0.15 mole sodium hydroxide are loaded into a reactor;after they are dissolved, 0.15 mole 2-acrylamide-2-methylpropanesulfonic acid is added and the mixture is stirred to homogeneousstate; the pH value of the system is adjusted to 7.0 with 10 mass %potassium hydroxide solution; then, 0.05 mole dendritic polymer monomerprepared in the Preparation Example 4, 0.30 mole 3-acrylamide propyldimethyl ammonium propylsulfonate, and 0.25 mole acrylamide are added,and the mixture is stirred to facilitate dissolving, so as to obtain areaction mixture solution; the reaction mixture solution is transferredinto a polymerization reactor, and 0.30 g ammonium persulfate and 0.30 gsodium bisulfite are added while stirring; the initial temperature ofpolymerization reaction is controlled at 40° C., and the reaction ismaintained for 90 min, to obtain a gelatinous elastic product; theobtained gelatinous elastomer is sheared, dried at 100° C., and ground,to obtain a polymer treating agent for drilling fluids. The apparentviscosity of 1 mass % water solution of the polymer treating agent fordrilling fluids is 42.5 mPa·s.

Performance test is carried out with the method described in Example 1,and the result is shown in Table 1 below.

Example 3 Preparation of Hyperbranched Copolymer

185 ml water and 0.1 mole sodium hydroxide are loaded into a reactor;after they are dissolved, 0.10 mole 2-acrylamide-2-methylpropanesulfonic acid is added into the reactor and the mixture isstirred to homogeneous state; the pH value of the system is adjusted to8.0 with 15 mass % sodium hydroxide solution; then, 0.20 mole dendriticpolymer monomer prepared in the Preparation Example 5, 0.30 mole3-acrylamide propyl (2-hydroxy)-propyl dimethyl ammonium chloride, and0.30 mole acrylamide are added, and the mixture is stirred to facilitatedissolving, so as to obtain a reaction mixture solution; the reactionmixture solution is transferred into a polymerization reactor, and 0.35g potassium persulfate and 0.35 g sodium bisulfite are added whilestirring; the initial temperature of polymerization reaction iscontrolled at 45° C., and the reaction is maintained for 60 min, toobtain a gelatinous elastic product; the obtained gelatinous elastomeris sheared, dried at 110° C., and ground, to obtain a polymer treatingagent for drilling fluids.

Performance test is carried out with the method described in Example 1,and the result is shown in Table 1 below. The apparent viscosity of 1mass % water solution of the polymer treating agent for drilling fluidsis 51 mPa·s.

Example 4 Preparation of Hyperbranched Copolymer

180 ml water and 0.1 mole sodium hydroxide are loaded into a reactor;after they are dissolved, 0.10 mole 2-acrylamide-2-methylpropanesulfonic acid is added into the reactor and the mixture isstirred to homogeneous state; the pH value of the system is adjusted to8.0 with 12 mass % potassium hydroxide solution; then, 0.20 moledendritic polymer monomer prepared in the Preparation Example 6, 0.35mole 3-acrylamide propyl dimethyl ammonium allylsulfonate, and 0.30 moleacrylamide are added, and the mixture is stirred to facilitatedissolving, so as to obtain a reaction mixture solution; the reactionmixture solution is transferred into a polymerization reactor, and 0.35g ammonium persulfate and 0.35 g sodium bisulfite are added whilestirring; the initial temperature of polymerization reaction iscontrolled at 45° C., and the reaction is maintained for 60 min, toobtain a gelatinous elastic product; the obtained gelatinous elastomeris sheared, dried at 120° C., and ground, to obtain a polymer treatingagent for drilling fluids. The apparent viscosity of 1 mass % watersolution of the polymer treating agent for drilling fluids is 53.5mPa·s.

Performance test is carried out with the method described in Example 1,and the result is shown in Table 1 below.

Comparative Example 1

A polymer treating agent for drilling fluids is prepared with the methoddescribed in Example 1, but the dendritic polymer monomer prepared inthe Preparation Example 3 is not added for polymerization reaction; inthat way, a reference polymer treating agent for drilling fluids isobtained. Performance test is carried out with the method described inexample 1, and the result is shown in Table 1 below.

TABLE 1 Comparative Polymer Treating Agent Example 1 Example 2 Example 3Example 4 Example 1 Dendritic polymer Preparation PreparationPreparation Preparation — monomer Example 3 Example 4 Example 5 Example6 Heat-resistance and 14.5 ml 13.7 ml 13.8 ml 18 ml 89 mlsalinity-resistance Inhibiting R₁, % 96.1 95.9 96.0 95.7 91.5 abilityR₂, % 95.4 95.1 95.1 94.5 80.2 R₂/R₁, % 99.27 99.17 99.06 98.75 87.65Viscocity retentivity, % 34.5 33.6 35.0 31.7 15.2 Note: The API filtrateloss is 228 ml after the base mud is treated by rolled aging for 16 h at180° C. The recovery rate of the clean water (without specimen) fordebris is 49.5%.

Examples 5-9

In Examples 5-9, a hyperbranched copolymer is prepared with the methoddescribed in Example 1 respectively, but the amphoteric ion monomer IIand oxidation-reduction initiating agent used in the preparation processare changed to those shown in Table 2 below. The apparent viscosityvalues of 1 mass % water solutions of the obtained polymer treatingagents for drilling fluids are 54.5 mPa·s, 53.0 mPa·s, 55.5 mPa·s, 54.0mPa·s, and 55 mPa·s respectively. Performance test is carried out withthe method described in example 1, and the result is shown in Table 3below.

TABLE 2 Example Exam- Exam- Example 5 Example 6 ple 7 Example 8 ple 9Amphoteric ion {circle around (1)} {circle around (2)} {circle around(3)} {circle around (4)} {circle around (5)} monomer Ini- Oxidizingpotassium tiator agent persulfate Reducer sodium sodium sodiumpyrosulfite thiosulfate sulfite Note: {circle around (1)}: 3-acryloxyethyl dimethyl ammonium propylsulfonate, {circle around (2)}: 3-acryloxyethyl diethyl ammonium propylsulfonate, {circle around (3)}: 3-acryloxyethyl diisopropyl ammonium propylsulfonate, {circle around (4)}:3-acrylamide propyl trimethyl ammonium chloride, {circle around (5)}:3-acryloxy propyl trimethyl ammonium chloride

TABLE 3 Polymer Treating Agent Example 5 Example 6 Example 7 Example 8Example 9 Dendritic polymer Preparation Preparation PreparationPreparation Preparation monomer Example 3 Example 3 Example 3 Example 3Example 3 Heat-resistance and 14.1 13.8 13.6 12.9 13.4salinity-resistance Inhibiting R₁, % 96.2 96.1 95.8 95.7 95.9 abilityR₂, % 95.5 95.2 95.1 94.9 95.1 R₂/R₁, % 99.27 99.06 99.27 99.16 99.17Viscocity 34.4 34.6 34.5 34.2 34.3 retentivity, % Note: The API filtrateloss is 228 ml after the base mud is treated by rolled aging for 16 h at180° C. The recovery rate of the clean water (without specimen) fordebris is 49.5%.

The results in Table 1 and Table 3 demonstrate that the polymer treatingagent in the present invention prepared from dendritic polymer monomerand other monomers has high heat-resistance and salinity-resistanceproperties, and favorable inhibiting ability, and the product has highwater-solubility.

While some preferred embodiments of the present invention are describedabove, the present invention is not limited to the details in thoseembodiments. Those skilled in the art can make modifications andvariations to the technical scheme of the present invention, withoutdeparting from the spirit of the present invention. However, all thesemodifications and variations shall be deemed as falling into theprotected domain of the present invention.

In addition, it should be appreciated that the technical featuresdescribed in the above embodiments can be combined in any appropriatemanner, provided that there is no conflict among the technical featuresin the combination. To avoid unnecessary iteration, such possiblecombinations are not described here in the present invention.

Moreover, different embodiments of the present invention can be combinedfreely as required, as long as the combinations don't deviate from theideal and spirit of the present invention. However, such combinationsshall also be deemed as falling into the scope disclosed in the presentinvention.

1. A dendritic polymer monomer, having a structure denoted by Z′-(Q)n-Y,wherein Z′ represents a structure denoted by the following formula (b),Q represents a dendritic constitutional repeating unit of the dendriticpolymer monomer, n represents a generation number of the dendriticpolymer monomer, and is an integer within a range of 2-6, and Yrepresents a group containing SO₃ ⁻ and COO⁻,

wherein R₁₄-R₁₆ are identical to or different from each other, and are Hor C₁-C₅ alkyl respectively.
 2. The dendritic polymer monomer accordingto claim 1, wherein Q has a structure denoted by the following formula(I), and Y has a structure denoted by the following formula (II),

wherein in formula (I), R₁ represents C₂-C₅ alkylene; R₂-R₄ can beidentical to or different from each other, and are H or C₁-C₅ alkylrespectively; in addition, for n structures denoted by formula (I),R₁-R₄ can be identical to or different from each other; in formula (II),R₈-R₁₃ can be identical to or different from each other, and are H orC₁-C₅ alkyl respectively; p and q can be identical to or different fromeach other, and are an integer within a range of 0-5 respectively; and Mis H, Na, or K.
 3. The dendritic polymer monomer according to claim 2,having a structure denoted by any of the following formulae (1), (2),(3) and (4),

wherein R₁-R₄, R₈-R₁₃, M, p, and q are in the same definitions as thosedescribed in claim
 2. 4. The dendritic polymer monomer according toclaim 2, wherein R₁ is CH₂CH₂; all of R₂-R₁₃ are H; M is Na or K; andboth p and q are 0 or
 1. 5. The dendritic polymer monomer according toclaim 3, wherein R₁ is CH₂CH₂; all of R₂-R₁₃ are H; M is Na or K; andboth p and q are 0 or
 1. 6. A hyperbranched copolymer comprisingdendritic structural units A, amphoteric ion structural units B,structural units C, and structural units D, and calculated in moles, aratio of dendritic structural unit A:amphoteric ion structural unitB:structural unit C:structural unit D being0.03-0.35:0.03-0.5:0.03-0.3:0.15-0.95, and an apparent viscosity of 1mass % water solution of the hyperbranched copolymer being 20-60 mPa·s,wherein the dendritic structural unit A has a structure denoted byZ′-(Q)n-Y, wherein Z′ represents a structure denoted by the followingformula (a1) or formula (a2), Q represents a dendritic constitutionalrepeating unit of the dendritic structure, n represents a generationnumber of the dendritic structure, and is an integer within a range of2-6, and Y represents a group that contains SO₃ ⁻ and COO⁻,

R₁₄-R₁₆ are identical to or different from each other, and are H orC₁-C₅ alkyl respectively; the amphoteric ion structural unit B has astructure denoted by the following formula (b1) or formula (b2), thestructural unit C has a structure denoted by the following formula (c),and the structural unit D has a structure denoted by the followingformula (d),

in formula (b1) and formula (b2), R¹, R², R³, R⁴ and R⁵ are H or C₁-C₃alkyl respectively, m and n are an integer with a range of 0-5respectively, and L is O or NH; in formula (b1), Y is COO⁻ or SO₃ ⁻; informula (b2), X⁻ is halogen anion, and R is H, OH, C₁-C₃ alkyl, orhydroxyl-substituted C₁-C₃ alkyl, in formula (c), R⁶, R⁷ and R⁸ are H orC₁-C₃ alkyl respectively, In formula (d), R⁹, R¹⁰, R¹¹, R¹² and R^(12′)are H or C₁-C₃ alkyl respectively, T is a bond or

M¹ is H or an alkali metal element, and y is an integer within a rangeof 1-4.
 7. The hyperbranched copolymer according to claim 6, wherein Qhas a structure denoted by the following formula (aI), and Y has astructure denoted by the following formula (aII),

wherein in formula (aI), R₁ represents C₂-C₅ alkylene, R₂-R₄ can beidentical to or different from each other, and are H or C₁-C₅ alkylrespectively; in addition, for n structures denoted by formula (aI),R₁-R₄ can be identical to or different from each other; in formula(aII), R₈-R₁₃ can be identical to or different from each other, and areH or C₁-C₅ alkyl respectively; p and q can be identical to or differentfrom each other, and are an integer within a range of 0-5 respectively;and M is H, Na, or K.
 8. The hyperbranched copolymer according to claim7, wherein the dendritic structural unit A has a structure denoted byany of the following formulae (A1), (A2), (A3) and A(4),

R₁-R₄, R₈-R₁₃, M, p, and q are in the same definitions as thosedescribed in claim
 7. 9. The hyperbranched copolymer according to claim8, wherein the dendritic structural unit A has a structure denoted byformula (A1) or formula (A3), and, in formula (A1) and (A3), R₁ isCH₂CH₂; all of R₂-R₄ and R₈-R₁₆ are H; M is Na or K; and both p and qare 0 or
 1. 10. The hyperbranched copolymer according to claim 6,wherein the amphoteric ion structural unit B is in one or more of thestructures denoted by the following formulae,


11. The hyperbranched copolymer according to claim 6, wherein thestructural unit D is in at least one of the structure denoted by thefollowing structural formulae,

wherein M¹ is H or an alkali metal element.
 12. The hyperbranchedcopolymer according to claim 9, wherein the amphoteric ion structuralunit B is

the structural unit C and the structural unit D are followingrespectively

wherein M¹ is H.
 13. The hyperbranched copolymer according to claim 6,wherein the ratio of dendritic structural unit A:amphoteric ionstructural unit B:structural unit C:structural unit D is0.05-0.25:0.05-0.3:0.05-0.15:0.25-0.65.
 14. A drilling fluid comprisinga water-based CaCl₂/polymer drilling fluid and the hyperbranchedcopolymer according to claim
 6. 15. A drilling fluid comprising awater-based CaCl₂/polymer drilling fluid and the hyperbranched copolymeraccording to claim
 7. 16. A drilling fluid comprising a water-basedCaCl₂/polymer drilling fluid and the hyperbranched copolymer accordingto claim
 8. 17. A drilling fluid comprising a water-based CaCl₂/polymerdrilling fluid and the hyperbranched copolymer according to claim
 9. 18.A drilling fluid comprising a water-based CaCl₂/polymer drilling fluidand the hyperbranched copolymer according to claim
 10. 19. A drillingfluid comprising a water-based CaCl₂/polymer drilling fluid and thehyperbranched copolymer according to claim
 11. 20. A drilling fluidcomprising a water-based CaCl₂/polymer drilling fluid and thehyperbranched copolymer according to claim 12.